1. Field of the Invention
The present invention relates to an optical disc device which plays back optical discs.
2. Description of the Related Art
Optical discs such as compact discs (CDs), digital versatile discs (DVDs), and Blu-Ray discs (BDs, registered trademark) have come to be widely used in recent years. Furthermore, optical disc devices have been put into practical use as devices for reading, recording, and playing back information recorded on optical discs, such as audio data and image data. Some examples of widely known optical disc devices are CD players, DVD players, BD players, and CD-ROM drives connected to personal computers.
Optical disc devices are equipped with optical pickups for irradiating optical discs with laser light and reading data from them. Optical pickups have laser diodes that shine laser light onto the data recording surface of optical discs affixed to turntables on which they rotate.
Optical pickups in turn have light detectors, such as photodiodes, for receiving reflected light from the data recording surface. Optical pickups convert light into electrical signals by using light detectors and provide these signals as output.
Accurate reading of data from the optical disc requires tracking to make the light axis of the laser light track the center of the pit string formed on the optical disc. To accomplish this, the optical pickup device is internally equipped with an actuator for driving the objective lens in the radial direction of the optical disc and a tracking servo to control the actuator.
Technology which superimposes high-frequency signals on the drive signals of the laser diode that shines the laser light has been seen in practical applications in such an optical disc device in order to improve the quality of the signal from the optical pickup and to enhance servo performance.
However, irradiation of the optical disc with a high-frequency laser leads to the deterioration of optical discs. When the optical disc device is paused during disc access and goes on standby for long periods of time, in particular, there is a problem in that the high-frequency laser is constantly shining and causes a rapid progression in optical disc deterioration.
An optical disc device which ensures durability under playback light by turning high-frequency superimposition off in idle mode has been disclosed and proposed in connection with the technology described above (for example, see Japanese Patent Application Laid-Open Publication No. 2011-159353).
However, with the disclosed technology, deterioration of optical discs can be reduced, but because high-frequency superimposition is completely stopped, servo characteristics decline. Therefore, there is a possibility of servo misalignment occurring continuously in standby states (i.e., in idle mode).